This invention relates to a plant controlling system for controlling a plant by a controller using a microcomputer, and particularly to a method of controlling a plant by integrating production and maintenance of the software and hardware of the system so as to provide information concerning the operation of the overall system for maintenance purposes, and maintenance apparatus to an operator thereof for accomplishing the same.
A controller using a microcomputer has been employed so as to facilitate designing, maintenance and adjustment of a plant controlling system. The plant controlling system based on hardware control is being gradually replaced by that based on software control.
However, hardware circuits are still used in the plant controlling system so as to ensure necessary minimum backup and protection of the system, so that the plant can keep its reliable operation or stop its operation without any inconvenience when the controlling system adopting a microcomputer is out of order. In addition, the plant controlling system includes sensors for detecting process signals or an operating unit for adjusting the amounts of processes.
FIG. 2 of the accompanying drawings shows an example of a fundamental configuration of a plant controlling system.
In FIG. 2, a controller 1 comprises a CPU2, a digital input card (referred to as DI card hereinafter) 3, a digital output card (DO card) 4, an analog input card (AI card) 5, an analog output card (AO card) 6, and a PI/O bus 7. A manual backup circuit 8 enables the continuous operation of a plant according to a command from an operation panel 9 which includes a manual operation designating unit and switches. The manual backup circuit permits the manual operation of the operating unit in an emergency due to malfunction of the controller or the like. In general, a plant 10 comprises a plurality of devices 11.
FIG. 3 shows the detailed fundamental configuration of a part of the controller of FIG. 2, which is associated with one particular device 11.
In FIG. 3, reference numeral 20 stands for functions, depicted as a circuit, to be carried out according to the software stored in a memory of CPU 2. Circuit elements 21, 24, 25, 27, 31, 33 are written by macro languages. The circuit element 21 is an input diagnosis macro, which diagnoses the status of process based on the rationality of a signal 22 fetched by the AI card, and outputs a logical signal 23 in case of abnormality. The circuit element 24 is a comparator, which compares the output of a control target setter (SET) 25 with the amount of process status, and outputs a deviation signal 26. The deviation signal 26 is inputted into a proportional integrator (P+I) 27, while being outputted from the AO card 6 to be indicated on a deviation indicator 28 on the operation panel 9. The proportional integrator 27 is set to either the automatic or manual control mode according to the automatic/manual logic signal 29 inputted through the DI card 3. In the automatic control mode, the proportional integrator 27 performs the proportional integration according to the deviation signal 26. In the manual mode, the proportional integrator 27 tracks the command signal 30 which is fetched via the AI card to be applied to the operation unit. The circuit element 31 is an output diagnosis macro, which compares the output from the proportional integrator 27 with the command signal 30, and checks the rationality of the signal with respect to sudden signal transformation, disconnection or the like. When detecting abnormality, the circuit element 31 issues a logical signal 32. The circuit element 33 is an OR macro, which outputs a signal indicative of the malfunction of the device in question according to the diagnosis macros 21 and 31 via the DO card 4.
A current/voltage converter 40 in the manual backup circuit 8 converts a current output, from a sensor 41 for detecting the amount of process status, into voltage. The output from the current/voltage converter 40 is inputted in the AI card 5, while being displayed on the indicator 42 provided on the operation panel 9. According to an output from the automatic/manual mode selecting logic 44, a signal selector 43 selects an output as follows:
In the automatic mode, the signal selector 43 selects an automatic operation output sent via the AO card 6 from the controller. In the manual mode, the signal selector 43 selects an output from a manual operation analog memory (AM) 45. The output from the signal selector 43 is inputted into a voltage/current converter 46, and serves as a signal for operating the operation unit 49 of the device, while being supplied to the AI card 5, and displayed on an indicator 47 on the control panel 9. An electricity pressure converter 48 converts the output from the voltage/current converter 46 into air pressure so as to control the operation unit 49. The mode of the analog memory 45 is selected according to the output from the automatic/manual mode selection logic 44. In the automatic mode, the analog memory 45 follows the output from the selector 43. In the manual mode, the output of the analog memory 45 is increased or decreased by a switch 50 on the operation panel 9. The automatic/manual mode selecting logic 44 selects either automatic or manual mode of the operation unit according to the control abnormality signal or the like outputted from the DO card 4 or operation of the automatic/manual mode selecting switch 51.
FIG. 4 illustrates an example of the automatic/manual mode selecting logic 44 shown in FIG. 3. The logic 44 includes an OR circuit 70, NOT circuits 71, and an AND circuit 72, all of which comprise hard wired logic.
As described above, the plant controlling system employing a controller adopting a microcomputer not only comprises software logic controlled by the controller but also comprises a variety of hardware such as the manual backup circuit 8, the operation panel 9 including a manual operation designating unit, switches, and devices 11.
To localize malfunction or to facilitate the maintenance work, the plant controlling system often adopts the distributed control method according to which one or more controllers 1 shown in FIG. 2 are employed.
In the plant controlling system employing a plurality of controllers, a maintenance apparatus is employed so as to perform software programming, to monitor operation of the controlling system and to tune parameters.
FIG. 5 shows an example of connection of a maintenance apparatus to the plant controlling system.
The maintenance apparatus 101 is connected to a channel 100 via which a plurality of controllers 1a to 1n are interconnected. Sometimes one controller is sufficient, and the maintenance apparatus may be connected to the controller by means other than the communication network. The maintenance apparatus 101 comprises a processing unit 102, a display unit 103 and an interactive operation unit 104.
In a conventional maintenance apparatus, the maintenance work is carried out by displaying only the software circuit 20 on the display unit 103, as illustrated in FIG. 6. Connection with the hardware outside the maintenance apparatus is known only from comments displayed on the screen of display unit 103 in association with input/output signal lines.
In addition, only a unit of minimum program executed by one controller, so-called one sheet, is displayed on the screen of the display unit 103 at a time because of limitations such as resolution of the display unit comprising a cathode ray tube (CRT).
Methods of displaying control circuits by means of logic symbols are exemplified in Japanese Patent Laid-Open Publications (KOKAI) Nos. 169804/1982 and 65510/1988, and U.S. Pat. No. 4,445,169.
In the related art, only the software circuits of the controller are displayed on the display unit of the maintenance apparatus as mentioned above. However since the plant controlling system has a variety of hardware besides the software circuits, a number of documents including shop drawings, operation manuals and so forth should be referred to so as to grasp the operation of the overall system.
With conventional plant controlling systems, the maintenance personnel are required to understand the overall system by referring to the above-mentioned documents first, and then perform the maintenance work by displaying the software circuits on the display unit of the maintenance apparatus. Therefore it is very difficult to perform quick and reliable maintenance work by using such a maintenance apparatus.
The controller has a plurality of sheets of the software circuits. Since the conventional maintenance apparatus displays only one sheet at a time, it is very difficult to grasp the overall flow of signals from the functional view point.
Moreover, when the plant controlling system comprises a plurality of controllers depending upon the scale and nature of the system, the controllers mutually exchange signals via communication paths so as to realize a certain control function. In such a case, it is very difficult to maintain the plant by grasping its overall functions since the maintenance apparatus can display the software circuits of only one controller at a time.
In addition, since the conventional maintenance apparatus aims at maintaining only the software regions of the controller, it is necessary to provide an additional controlling system for preparing documents to perform the maintenance work of the controller including the hardware regions.